Why is a Charlie Horse (leg cramp) called a Charlie Horse?
The origin of this phrase is somewhat unclear. One theory is that it originated with a common occupational hazard of constables. Constables were called “Charleys” in 17th century England and aching legs were a part of the job. It’s also possible that the phrase came into usage after a lame horse named Charley pulled a roller across a Chicago White Sox ballpark in the 1890s, and the term stuck to described a common malady among baseball players.